One of the most serious problems afflicting vehicles that use fossil fuels such as, for example, gasoline and diesel, is the resultant air pollution. As a solution to solve this problem, attention is being paid to technology that uses a secondary battery, which may be charged or discharged, as a power source for a vehicle. Thereby, for example, electric vehicles (EV), which move using only a battery, and hybrid electric vehicles (HEV), which use a battery and an existing engine together, have been developed, and some of them have been commercialized. Although a nickel metal hydrogen (Ni-MH) battery is mainly used as a secondary battery serving as the power source of, for example, an EV and a HEV, the use of, for example, a lithium ion battery has recently been attempted.
In order to be used as the power source of, for example, an EV and a HEV, the secondary battery must have a high output and a large capacity. To this end, a plurality of small secondary batteries (unit batteries) may be connected to one another in series, or in some cases, may be connected in series or parallel with one another so as to constitute a battery cell module.
FIG. 1 is a conceptual view illustrating one example of a battery pack for an electric vehicle in accordance with the related art, FIG. 2 is a perspective view illustrating a battery cell module, which constitutes the battery pack of FIG. 1, FIG. 3 is an exploded perspective view illustrating the battery cell module of FIG. 2, and FIG. 4 is a conceptual view illustrating deterioration in cooling performance attributable to the shape of the battery cell module.
One example of the battery pack for the electric vehicle in accordance with the related art, as illustrated in FIGS. 1 to 3, includes frame assemblies 5A and 5B, which are arranged parallel with each other in order to install a plurality of battery cell modules 20A, 30A and 40A inside a battery carrier (not illustrated), a mounting tray 7 disposed above the frame assemblies 5A and 5B, and a battery pack cover 10, which covers the top of the battery carrier and the battery cell modules 20A, 30A and 40A, which are horizontally arranged parallel with one another, or are vertically stacked one above another above the mounting tray 7.
Here, cooling plates 20B, 30B and 40B are disposed on the underside of the respective battery cell modules 20A, 30A and 40A in order to remove heat generated from the battery cell modules 20A, 30A and 40A. The cooling plates 20B, 30B and 40B serve to cool the battery cell modules 20A, 30A and 40A upon receiving coolant through a coolant hose (not illustrated).
Each of the battery cell modules 100; 20A, 30A or 40A, as illustrated in FIGS. 2 and 3, includes a plurality of secondary batteries 110, which are vertically upright and are arranged parallel with one another in the left-and-right direction by a long length, and a first end plate 120A and a second end plate 120B, which are arranged at opposite ends of the battery cell module and are coupled respectively to outermost secondary batteries 110 so as to come into close contact with the same. The battery cell module 100 has an approximately rectangular shape that is elongated in the left-and-right direction, and an internal circuit board (ICB) 130 is disposed on the remaining side surface portion excluding the first end plate 120A and the second end plate 120B.
In the secondary batteries 110, which are arranged parallel with one another in the left-and-right direction by a long length, each unit battery consists of a battery 111, which serves as an anode, and a battery 112, which serves as a cathode. The respective batteries are attached to one another using a plurality of long bolts 140, which longitudinally penetrate into corner portions of the batteries, so as to construct a single battery cell module 100.
However, in the example of the battery pack for the electric vehicle in accordance with the related art, as illustrated in FIG. 4, a prescribed gap may be formed between the battery cell module 100; 20A, 30A or 40A and the cooling plate 8; 20B, 30B or 40B, which is provided to cool the battery cell module 100; 20A, 30A or 40A, attributable to the shape of the receiving space defined inside the battery carrier, or deformation of the lower surface of the battery cell module 100; 20A, 30A or 40A due to the intrinsic weight thereof. The gap may deteriorate cooling performance.
More specifically, although a thermal pad 9 is disposed so as to prevent a gap from being formed between the lower surface of the battery cell module 100; 20A, 30A or 40A and the cooling plates 8; 20B, 30B or 40B, as illustrated in (a) of FIG. 4, in the case where the lower surface of the battery cell module 100; 20A, 30A or 40A is shaped to be convex upward, the central portion of the cooling plate 8; 20B, 30B or 40B, which is in surface contact with the lower surface of the battery cell module 100; 20A, 30A or 40A, may sag due to the intrinsic weight thereof because the cooling plate 8; 20B, 30B or 40B is elongated in the left-and-right direction. Thereby, ae gap, which deteriorates cooling performance, may be formed between the upper surface of the thermal pad 9 and the lower surface of the battery cell module 100; 20A, 30B or 40A. In addition, as illustrated in (b) of FIG. 4, in the case where the lower surface of the battery cell module 100; 20A, 30A or 40A is shaped to be concave downward, opposite left and right end portions of the battery cell module 100; 20A, 30A or 40A may sag due to the intrinsic weight thereof. Thereby, a gap as described above may be formed between the upper surface of the thermal pad 9 and the lower surface of the battery cell module 100; 20A, 30B or 40A, which causes deterioration in cooling performance.